1. Field of the Invention
The present invention relates to alkane sulfonates useful as viscosity regulators for highly viscous anionic surfactant concentrates.
2. Description of Related Art
The starting materials used in the commercial manufacture of powder-form or granular detergents and cleaners by the hot-spraying process are aqueous suspensions or slurries which contain a high percentage of or even all the detergent ingredients. It is important for economic reasons that these slurries should be rich in detergent ingredients with very little liquid ballast. Accordingly, the smallest possible quantity of water is used for preparing the slurries. However, limits are imposed on the level of concentration by the highest possible viscosity at which the slurries can still just be processed.
An essential constituent of most detergents and cleaners are anionic surfactants which, in the preparation of the detergent slurries, are generally used in the form of their alkali metal or ammonium salts concentrated to pastes. In the case of the sodium salts of .alpha.-sulfotallow fatty acid methyl ester for example, the surfactant content of the paste-form concentrates is of the order of 30% by weight. Pastes of higher surfactant content can only be processed with considerable difficulty, if at all. One feature of the rheological behavior of these anionic surfactant concentrates is that they do not react to the addition of water by a reduction in viscosity, but instead with an increase in viscosity to a gel-like state which presents the processor with further problems, for example in the blockage of valves and pipes or in the fact that the gelatinous lumps formed can only be redissolved after mechanical size reduction.
Various proposals have already been put forward with a view to solving these problems. Thus, U.S. Pat. No. 3,893,955, for example, describes the salts of certain carboxylic acids, more especially salts of hydroxy carboxylic acids, as viscosity regulators. According to U.S. Pat. No. 3,899,448, sulfonated aromatic compounds are suitable for this purpose. British Pat. No. 1,437,089 discloses sulfates or sulfonates of aliphatic, optionally substituted C.sub.1 -C.sub.6 hydrocarbons as viscosity regulators. These publications also mention the addition of lower alcohols as a possibility for reducing viscosity. Other publications describe the addition of the well known hydrotropes, such as for example cumene sulfonate, or of acidic phosphoric acid esters (U.S. Pat. No. 3,741913), polyhydric alcohols, certain carboxylic acids and/or esters of these compounds (U.S. Pat. No. 4,239,641). The use of sulfates of certain polyalkylene ether glycols for improving the flow behavior of anionic surfactant concentrates is known from U.S. Pat. No. 4,384,978.
Some of the additives mentioned in the literature do not work with all surfactant concentrates; some have to be used in high concentrations; while others, such as lower alkanols for example, lower the flash point of the concentrates.